Whipworms

How they spread:
A female whip worm can produce 2,000 eggs a day. Eggs are passed in feces, and can survive for years in the soil. Whip worms are very difficult to eradicate.

Adult whipworms look like pieces of thread with one end enlarged. They live in the cecum, the first section of the dog's large intestine. Infestations are usually light, so an examination of feces may not reveal the presence of eggs. Several checks may be necessary before a definitive diagnosis can be made.